A Little BackgroundRegular followers of my YouTube channel know that I recently diagnosed and repaired a faulty knock sensor on my Porsche 986... The knock sensors retard (slow down) timing for low octane fuel. This prevents knocking from occurring in the Boxster's high compression (11:1) engine. I assumed the engine would default to a retarded timing setting if it knew one knock sensor was bad. With this in mind, I logged data from my car with a faulty knock sensor, then collected more data once the knock sensor worked. Since this was all done on the street, the two runs are not identical, but they show a clear advance in timing with a working knock sensor.
The Nerdy Charts
|A little messy, because 4 charts are stacked, but the green arrow indicates the advanced timing with the working knock sensor.|
|Ignition Timing with the good sensor (measured in milliseconds)|
|Ignition Timing with the bad knock sensor (measured in milliseconds)|
For those of you who have access to Photoshop, I have these and many other graphs loaded as layers in this PSD. The file must be downloaded and opened in Photoshop to view all the layers of nerdy charts.